Development of the superoxide generating system. We will determine the activity of NADPH oxidase and the amount of membrane cytochrome b at various stages of HL-60 differentiation. Levels of the selenoenzyme glutathione peroxidase will be measured in cells grown with and without selenium and the effects determined of such manipulation on the respiratory burst. Degranulation. We have found that HL-60 cells do not contain lactoferrin and contain decreasing amounts of myeloperoxidase as they mature. We will incubate cells in 35S-methionine and measure incorporation into lactoferrin, myeloperoxidase, and lysozyme (a positive control - its concentration increases) specifically separated by immunoprecipitation. We will continue to adapt the long-term bone marrow culture system to human marrow in order to study the in vitro differentiation of normal myeloid cells and compare the results to those obtained with the HL-60 model. We will manipulate cyclic nucleotide levels and inhibit transmethylation reactions in order to study their effects on normal differentiation. Investigation of disease states such as congenital neutropenia, Chediak-Higashi syndrome, and chronic granulomatous disease would also be possible.